1. Technical Field
This invention relates to a method and an apparatus for mixing or dispersing particles based upon the principle of a contact type electric field curtain.
2. Background Art
A prior contact type electric field curtain is comprised of a train of electrodes and of a dielectric layer placed in close vicinity of or in contact with the electrodes, as disclosed in Japanese Patent Publication Kokoku No. 54-12667 "A Method Of Constructing A Contact Type Electric Field Curtain And An Apparatus With Use Therewith". The electric field curtain is adapted in operation to permit a lightweight substance on the dielectric layer to have thereon electric charges induced by contact thereof with the electric layer and to be rendered to electrodynamical force afforded by the electric field curtain. So that the lightweight substance is thereby repelled and driven.
Referring to FIG. 9, the arrangement described above is illustrated.
Electrodes a, which are rod-shaped or donut-shaped, for forming an electric field curtain are aligned, and spaced from each other. Alternating voltage b is applied between the adjacent electrodes for an alternating non-uniform electric field having electric force lines indicated by dotted line c around the respective electrodes a. The alternating non-uniform electric field changes its magnitude and direction with respect to space, while with respect to time it changes its direction sinusoidally.
As charged particles approach the alternating non-uniform electric field, the particles are the influence of alternating electric force along the line of electric force, c and hence are forced to oscillate substantially along the curved line of electric force c, whereby the charged particles are rendered to puroduce a, outward centrifugal force which is perpendicular to the lines c each half period of the oscillation. Those particles are thus subjected to mean centrifugal force Fc.
Each particles is is subjected, at a location close to the electrode a where the electric field is stronger, to the electric force oriented to go away from the electrode a, while being subjected, at a location far from the electrode a where the electric field is weaker, to the electric force oriented toward the elctrode a. This is because the particles oscillate in a viscous medium. Either way, as a result of the difference therebetween, the particle is rendered to the mean gradient force Fg directed along the line of electric force, c going away from the electrode a.
The mean centrifugal force Fc is produced owing to a spatial change (curved configuration) of the direction of the electric force line c, while the gradient force Fg is produced due to a spatial change of the density of the lines c (a gradient of electric field intensity). Both are produced because of the electric field being non-uniform and alternate. Thus, the particle is subjected to composite force formed therein, i.e., electrodynamic repulsion force Fr in the direction going away from the electrode train.
The particles adhering to the dielectric layer when the latter is taken into the electric field are charged immediately with electricity on the basis of the principle of the contact charge and forced to float from the dielectric layer owing to the aformentioned electrodynamical repulsion force.
Such a contact type electric field curtain apparatus finds application in electrostatic precipitators, electrostatic coating booths, and electrostatic guns, where particles have to be swept off or moved by a repulsion force.
The present inventioh has been devised based on recognition of the fact that any particle present in the action area of the electric field curtain is subjected to violent disturbance.